Characteristics Of Cavity Research Articles

Effect of melting combined with ice recrystallization on porous starch preparation: Pore-forming properties, granular morphology, functionality, and multi-scale structures

In this work, critical melting (CM) combined with freeze-thawing treatment (FT, freezing at −20 ℃ and −80 ℃, respectively) was used to prepare porous starch. The results showed that CM combined with the slow freezing rate (−20 ℃) can prepare porous starch with characteristics of grooves and cavities, while combined with the rapid freezing rate (−80 ℃) can prepare with holes and channels, especially after repeating FT cycles. Compared with the native counterpart, the specific surface area, pore volume, and average diameter of CMFT-prepared porous starch were significantly increased to 4.07 m2/g, 7.29 cm3/g × 10−3, and 3.57 nm, respectively. CMFT significantly increased the thermal stability of starch, in which the To, Tp, and Tc significantly increased from 63.32, 69.62, and 72.90 (native) to ∼69, 72, and 76 °C, respectively. CMFT significantly increased water and oil absorption of porous starch from 91.20 % and 72.00 % (native) up to ∼163 % and 94 %, respectively. Moreover, CMFT-prepared porous starch had a more ordered double-helical structure, which showed in the significantly increased relative crystallinity, semi-crystalline lamellae structure, and the proportion of the double helix structure of starch. The synergistic effect of melting combined with ice recrystallization can be used as an effective way to prepare structure-stabilized porous starch.

Discovery of piperonyl-tethered sulfoximines as novel low bee-toxicity aphicides targeting Amelα1/ratβ2 complex

Nicotinic acetylcholine receptor (nAChR) is recognized as a significant insecticide target for neonicotinoids and some agonists. In this study, the nAChR α1 subunit from Apis mellifera was first found to be narrowly tuned to different bee toxicity insecticides, namely, sulfoxaflor (SFX) and flupyradifurone (FPF). Hence, novel sulfoximine derivatives 7a-h were rationally designed and synthesized by introducing a benzo[d][1,3]dioxole moiety into a unique sulfoximine skeleton based on the binding cavity characteristics of Amelα1/ratβ2. The two electrode voltage clamp responses of 7a-h were obviously lower than that of SFX, indicating their potentially low bee toxicity. Besides, representative compounds 7b and 7g exhibited low bee toxicity (LD50 > 11.0 μg/bee at 48 h) revealed by acute contact toxicity bioassays. Molecular modelling results indicated that Ile152, Ala151, and Val160 from honeybee subunit Amelα1 and Lys144 and Trp80 from aphid subunit Mpα1 may be crucial for bee toxicity and aphicidal activity, respectively. These results clarify the toxic mechanism of agonist insecticides on nontargeted pollinators and reveal novel scaffold sulfoximine aphicidal candidates with low bee toxicity. These results will provide a new perspective on the rational design and highly effective development of novel eco-friendly insecticides based on the structure of the nAChR subunit.

Collapse risk evaluation of subsurface cavities and development of rational countermeasures considering road structure and cavity characteristics.

Collapse risk evaluation of subsurface cavities and development of rational countermeasures considering road structure and cavity characteristics.

Macromorphoscopic study of the orbital cavities of human dry skulls for sex estimation

Sex estimation was analyzed from the orbital cavities of 304 dry skulls (148 female and 156 male), which were classified as rectangular, circular, and rhomboid. Logistic regression was performed to estimate the probability of the orbital cavity belonging to males or females. In decreasing order, there was a higher occurrence of rectangular, rhomboid, and circular shapes. The estimation of sex resulted in an overall percentage of correctness of 59.9%. The left orbital cavity presented a significant p-value, but the chance of the characteristics of this orbital cavity being considered as predictors for sex was only 0.64 times higher. The morphology of the orbital cavity can provide information for the elaboration of the biological profile. However, studies are still needed to allow the possible use of its anatomy to estimate sex in the Brazilian population.

Experimental Study on the Ignition Characteristics of Scramjet Combustor with Tandem Cavities Using Micro-Pulse Detonation Engine

This experimental investigation focused on the ignition and combustion characteristics of a tandem cavity-based scramjet combustor with side-by-side identical cavities. This study utilized the Pusan National University-direct connect scramjet combustor (PNU-DCSC), which was capable of simulating flight conditions at Mach number 4.0–5.0 and altitudes of 20–25 km using the vitiated air heater (VAH). The combustion tests were conducted under off-design point conditions corresponding to low inlet enthalpy. It is a condition in which self-ignition does not occur, and a micro pulse detonation engine (μPDE) ignitor is used. The results revealed that as the injection pressure of the gaseous hydrogen fuel (GH2) and the corresponding equivalence ratio increased, the combustion mode transitioned from the cavity-shear layer flame to the jet-wake flame. Furthermore, the measured wall static pressure profiles along the isolator and scramjet combustor indicated that the region of elevated pressure distribution caused by the shock train expanded upstream with higher equivalence ratios. When ignited from the secondary cavity, the combustion area did not extend to the primary cavity at lower equivalence ratios, while it expanded upstream faster with higher equivalence ratios. Therefore, the combustion characteristics of the tandem cavity were found to vary based on the overall equivalence ratio of the main fuel (GH2) and ignition position.

Optimizing Absorption for Intranasal Delivery of Drugs Targeting the Central Nervous System Using Alkylsaccharide Permeation Enhancers.

Intranasal delivery of drugs offers several potential benefits related to ease of delivery, rapid onset, and patient experience, which may be of particular relevance to patients with central nervous system (CNS) conditions who experience acute events. Intranasal formulations must be adapted to address anatomical and physiological characteristics of the nasal cavity, including restricted dose volume, limited surface area, and barriers to mucosal absorption, in addition to constraints on the absorption window due to mucociliary clearance. Development of an effective formulation may utilize strategies including the addition of excipients to address the physicochemical properties of the drug within the constraints of nasal delivery. Dodecyl maltoside (DDM) and tetradecyl maltoside are alkylsaccharide permeation enhancers with well-established safety profiles, and studies have demonstrated transiently improved absorption and favorable bioavailability of several compounds in preclinical and clinical trials. Dodecyl maltoside is a component of three US Food and Drug Administration (FDA)-approved intranasal medications: diazepam for the treatment of seizure cluster in epilepsy, nalmefene for the treatment of acute opioid overdose, and sumatriptan for the treatment of migraine. Another drug product with DDM as an excipient is currently under FDA review, and numerous investigational drugs are in early-stage development. Here, we review factors related to the delivery of intranasal drugs and the role of alkylsaccharide permeation enhancers in the context of approved and future intranasal formulations of drugs for CNS conditions.

Thermodynamic characteristics of the hot-temperature cavity generated by the spark discharge in saline water

Spark discharge in saline water can generate cavity oscillating violently. However, the thermodynamic characteristics of such a cavity is still unclear owing to the complex mechanism behind it. In this study, a systematic model is developed with the considerations of thermal radiation and mass transport, which can successfully evaluate the thermodynamic properties of the spark-induced cavity in saline water. The physical parameters related to the mass transport are identified by comparing with the experimental measurements. By using the validated parameters, we find that the thermal radiation and the condensation process cannot be ignored, and the number of water molecule increases at the first collapse point. In addition, the maximum cavity size increases with increasing absorption of thermal radiation, but decreases when the condensation coefficient increases. Increasing the discharge energy and ambient temperature are found to help generate larger cavity. The inner temperature and pressure at the collapse phase increases with the increase of the discharge energy, whereas decreases when the ambient temperature increases. Furthermore, the minimum temperature at the first maximum size is up to 3000 K under 0.1 MPa, and reaches 8000 K when the ambient pressure is larger than 1 MPa. Thus, we believe the spark-induced cavity in saline water is hot, at least during the first oscillation cycle.

Dynamic Pressure Measurements in a Rectangular Cavity with Multiple Stores

An experimental investigation is carried out to study the effects of Mach number on the acoustic resonance characteristics of a rectangular cavity with and without multiple stores. Measurements are conducted for a cavity with a length-to-depth ratio of 4.5 at Mach numbers of 2, 3, 4, and 5. Dynamic pressures are measured within the cavity and on the store surfaces. An increase in Mach number results in a decrease in overall sound pressure levels at all measurement locations within the cavity. Pressure spectra indicate that increasing the Mach number decreases both the peak and broadband amplitudes of the cavity pressure fluctuations. At Mach 5, the amplitude of the cavity modes is significantly reduced in the upstream half of the cavity, and the modes are either indistinguishable from broadband levels or absent in the downstream half. The addition of stores reduces cavity acoustics, with two stores offering greater reduction than a single store. The effect of Mach number and the presence of stores on the aeroacoustic feedback loop in a cavity align with literature. Additionally, the pressure fluctuations on the windward store surface scale with Mach number in a similar trend as the cavity acoustics.

Antimicrobial effect of Streptococcus salivarius outer membrane-coated nanocomplexes against Candida albicans and oral candidiasis

Oral mucosal infection, especially oral candidiasis, is currently the most common oral mucosal disease. Traditional drug treatment regimens have difficulty adhering to mucous membranes, coupled with the unique anatomical and physiological characteristics of the oral cavity, thus reducing drug availability and limiting the effective time of drug action. Inspired by cell membrane-coated nanoparticles, this study aimed to construct a bionic adherent oral mucosal drug delivery system and investigated its therapeutic potential for oral candidiasis. The system was obtained by encapsulating Streptococcus salivarius K12 membranes on triclosan-loaded PLGA nanoparticles using an extrusion method. The constructed nanocomplexes (K12/TCS@PLGA-NPs) inherited the properties of the source cell membrane, bionically adhering to the oral mucosa and binding to the candida albicans hypha. Our in vitro and in vivo experiments have confirmed that K12/TCS@PLGA-NPs nanocomplexes significantly inhibits the formation of C. albicans biofilms and the development of oral candidiasis by enhancing the accumulation of drugs in lesions, optimizing drug efficacy. Furthermore, the biomimetic nanocomplexes could be considered safe and effective drug delivery systems, which hold considerable therapeutic promise for oral mucosal infections including candidiasis.

Unravelling Peritoneal Carcinomatosis Using Cross-Sectional Imaging Modalities

Peritoneal carcinomatosis (PC) refers to malignant epithelial cells that spread to the peritoneum, principally from abdominal malignancies. Until recently, PC prognosis has been considered ill-fated, with palliative therapies serving as the only treatment option. New locoregional treatments are changing the outcome of PC, and imaging modalities have a critical role in early diagnosis and disease staging, determining treatment decision making strategies. The aim of this review is to provide a practical approach for detecting and characterizing peritoneal deposits in cross-sectional imaging modalities, taking into account their appearances, including the secondary complications, the anatomical characteristics of the peritoneal cavity, together with the differential diagnosis with other benign and malignant peritoneal conditions. Among the cross-sectional imaging modalities, computed tomography (CT) is widely available and fast; however, magnetic resonance (MR) performs better in terms of sensitivity (92% vs. 68%), due to its higher contrast resolution. The appearance of peritoneal deposits on CT and MR mainly depends on the primary tumour histology; in case of unknown primary tumour (3–5% of cases), their behaviour at imaging may provide insights into the tumour origin. The timepoint of tumour evolution, previous or ongoing treatments, and the peritoneal spaces in which they occur also play an important role in determining the appearance of peritoneal deposits. Thus, knowledge of peritoneal anatomy and fluid circulation is essential in the detection and characterisation of peritoneal deposits. Several benign and malignant conditions show similar imaging features that overlap those of PC, making differential diagnosis challenging. Knowledge of peritoneal anatomy and primary tumour histology is crucial, but one must also consider clinical history, laboratory findings, and previous imaging examinations to achieve a correct diagnosis. In conclusion, to correctly diagnose PC in cross-sectional imaging modalities, knowledge of peritoneal anatomy and peritoneal fluid flow characteristics are mandatory. Peritoneal deposit features reflect the primary tumour characteristics, and this specificity may be helpful in its identification when it is unknown. Moreover, several benign and malignant peritoneal conditions may mimic PC, which need to be considered even in oncologic patients.

Experimental Study on Motion Characteristics of Cavity Attached to the Tail of Underwater Vehicle

The formation and development of an attached cavity at the tail of an underwater moving vehicle involves a complex multiphase flow, which determines the load characteristics and motion stability of the vehicle. In this study, an experimental method was used to explore the formation process and motion characteristics of the cavity at the tail of the vehicle, and a pressure sensor installed at the tail of the model was used to establish the relationship between the evolution of the tail attachment cavity and transient pressure. The study found that the process of pulling and breaking the attached cavity was accompanied by the generation of bidirectional jets, and reducing the cavitation number could weaken the occurrence of jet impact. When the ventilation flow reaches the critical value Q¯in = 1.28, the cavity pulsates. In addition, increasing the ventilation flow does not increase the size of the tail cavity, and the length of the cavity at the closure increases with the decrease of the cavitation number.

Experimental study on ballistic stability of truncated cone projectile in high-speed oblique water entry

In this paper, the high-speed photography technique was used to study the high-speed oblique water entry of truncated cone projectiles, and the effects of nose shape, projectile velocity and entry angle on the cavity and ballistic characteristics of oblique water entry were discussed. The experimental results show that the influence of nose shape on the oblique water entry cavity and ballistic characteristics is related to the nose wetted area. For the same type of projectile, with the increase of projectile velocity, the cavity size becomes larger at the same penetration displacement and the surface closure time gets longer. Moreover, with the increase of entry angle, the surface closure time decreases, the velocity attenuation gets faster, at the same penetration displacement the cavity opening length becomes shorter and the cavity asymmetry weakens. Additionally, the results indicate that the trajectory stability of the truncated cone projectile varies under different water entry velocities and attitude angles.

Host-guest assembly functionalization through molecular selective adsorption into chiral Kagome-like frameworks

Supramolecular self-assembly offers a feasible route for nanopatterning and functionality. The construction and precise control of selective adsorption at the molecular scale play essential roles in fundamental sciences and practical applications. Molecular tiling such as trihexagonal tiling Kagome networks has potential promising chemical and physical properties. Distorted Kagome-like networks controllable fabrication is possible by coupling molecular functional groups and substrate atoms. A chiral Kagome-like network was constructed using IFDO ([1,2-b]fluorene-6,12-dione) as precursor molecules complemented with molecular beam epitaxy and annealing strategies. Revealing arrangements of the assembled network of O-Cu metal coordination linked Kagome-like networks on the Cu(111) surface and their assembly mechanisms and cavity characteristics were explored in detail through scanning tunneling microscopy combined with density functional theory. Based on the electronic state difference between the hole center of the network and the molecular backbone, the host–guest network was successfully prepared by co-depositing C60 molecules. Kagome-like networks could as an efficient template for regulating the adsorption configuration of C60. Our results demonstrate a controllable and efficient method to design atomically precise ordered host–guest assemblies on solid surfaces, advancing the approach is yet another step toward the fabrication of molecular devices.

Flow characteristics of a trapped-vortex pilot cavity under the influence of radial structure

In this study, using a laboratory-scale combustor model, we examined the flow modes in the trapped-vortex cavity under the influence of a radial bluff-body structure by particle image velocimetry (PIV) technology. The tested area included both inside the cavity and the mainstream zone. It is found that, under different inlet parameters, structure width, and circumferential positions, the flow characteristics change significantly for this structure. The number of vortexes, the distribution of vorticity, and the Q-value differ at different circumferential positions; while the increase in radial structure width, incoming flow velocity, and total pressure will all lead to stronger vortex flow. The flow pattern inside the cavity and behind the radial structure are coupled with each other, forming six typical flow modes. Further theoretical analysis summarized the causes of the six flow modes according to two aspects: how the mainstream influences the cavity flow, and the influence degree of the mainstream on the cavity flow. Considering the effect of the radial structure, the mainstream at different positions will have different effects on the cavity, which can be represented by the ratio of the radial position to the width of the structure. The influence degree was related to the inlet parameters and the width of the radial structure, which can be represented by the dynamic pressure of cavity inlet jets.

Examination of air flow characteristics over an open rectangular cavity between the plates

Air flow characteristics of an open cavity have been numerically examined by using different turbulence models of Detached Eddy Simulation (DES), k-ε Realizable, k-ω Shear Stress Transport (SST) and Large Eddy Simulation (LES) based on an experimental study of open literature. Numerical results of transient analyses have been compared to experimental results at cavity length-based Reynolds number of Re = 4600. Pressure distributions, streamline patterns, streamwise velocity components, mean velocity values and their vectors have been given in terms of contour graphics. Moreover, velocity profiles have been presented. Pressure fluctuations have been triggered by flow separation and its reattachment. Due to upstream separation of boundary layer, there was curved boundary layer obtained between the outer potential-flow-like and the recirculation zones. As a result, negative velocity values are evidence for rotational flows affected by formation of secondary flows in the cavity. Furthermore, lower pressure region has been observed as a result of rotational flow which was powerful in the open cavity. Numerical results of DES and LES turbulence models are in good agreement with the results of reference study. As the numerical results obtained by LES turbulence model are approximately same with those of experimental reference study, LES turbulence model is mostly recommended. As an option to these turbulence models, k-ω SST model could be utilized for limited computer capacity. However, k-ε Realizable model is not sufficient for capturing rotational flows which are very effective in terms of present case.

Finesse measurement for high-power optical enhancement cavity

Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity (OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range (FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down (CRD) method, the rapidly swept-frequency (SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.

Radiation Effect on Heat Transfer in Narrow Cavities

The thermal comfort and air-conditioning energy consumption of vehicles or trains are dependent on the thermal resistance of its envelopes, which could be enhanced by improving the radiation characteristics of the narrow cavities scattered in their envelopes. However, the study for a feasible method and its effectiveness has been given little attention. This paper introduces a method that involves pasting aluminum foil on the inner wall to change the radiation characteristics of the narrow cavity and analyzed its effects on narrow-cavity heat transfer by experimental and numerical methods. The results indicate that the radiation effect on heat transfer in a narrow cavity made of conventional material is dominant, with a rate larger than 75%, and that pasting aluminum foil is an effective and feasible method of weakening the radiation rate in narrow-cavity heat transfer, decreasing it to less than 10%. This paper will provide a reference to improve the insulation characteristics of vehicle enclosure.

Investigation on the flow-induced tangential force characteristic of labyrinth seals under different operation parameters

The flow-induced tangential force Ft is crucial for the annular gas seal stability. In this paper, a three-dimensional CFD model is established to study the Ft characteristics of the labyrinth seal. The overall Ft of the seal section is decomposed into each seal cavity. The Ft characteristic of each seal cavity versus rotation speed ω and inlet pressure pin is analyzed. The result shows that the sign of Ft in each seal cavity changes from the negative to the positive along the leakage direction, resulting in a specific crossing tooth number Nc at which Ft≈ 0 N. When the tooth number is smaller than Nc, the seal stability increases with the increase of ω and pin. When the tooth number is larger than Nc, the trend is reversed. When the tooth number equals Nc, the seal stability is in a critical state, showing no dependency to the ω and pin. The Nc is a novel index for the labyrinth seal stability.

Breeding ecology, population size and nest site preferences of Red-billed Tropicbirds at St Helena, South Atlantic Ocean

ABSTRACT We describe the population size and breeding ecology of the Red-billed Tropicbird, Phaethon aethereus, a poorly studied pantropical seabird, at St Helena, South Atlantic. The population size of 81–246 pairs and 272–564 individuals identifies the study population as the largest colony of Red-billed Tropicbirds in the South Atlantic, but also an internationally important part of the global population. We estimated the survival from laying to fledging of 158 nests between 2004 and 2017 at only 33%, among the lowest values reported globally for the species. Most nest failures occurred during incubation, with predation identified as the predominant cause of fledging failure. Intervals between breeding attempts were longer after successful nesting attempts than failed attempts. Previous breeding interval and nest cavity fidelity further influenced the interval between breeding attempts, while the presence of replacement clutches did not. Multiple nest site and cavity characteristics were important predictors of cavity use, nest site selection and productivity. Management options for reducing mammalian predators to ensure the long-term viability of this important population at St Helena are discussed.

Synergistic effects of vapor and gaseous cavitation and mass-transfer mechanism in a mechanical pump

Dynamic gas–liquid mass-transfer processes are extensively encountered in gas–liquid mixture transport systems, where mechanical pumps pressurize the mixture and are accompanied by flow and mass-transfer instabilities. Herein, our proposed gaseous cavitation model was innovatively developed to revolutionize the independent unidirectional absorbed or evolved mass transfers. Complex gas–liquid behaviors under the synergetic effects of gaseous and vapor cavitations were achieved for the first time in an on-orbit refueling mechanical pump. Four coupled mass-transfer processes, namely, evolution, evaporation, absorption, condensation, and gas–liquid distribution, were investigated through numerical calculations. The results indicated that when the solution was close to critical saturation and conversion of the mass-transfer direction, a surge in the mass-transfer rate, and more intense hydrodynamic instability occurred. The vapor drove the accumulation of the evolved gas along the edge of the vapor in the impeller, where the evolved-dominated mass-transfer bands existed on the suction surfaces of the long blade, exhibiting the degassing characteristics of the vapor cavity, and other regions belonged to absorption-dominated region. Continuous dissolution induced by significant positive pressure gradient led to the maximum absorbed oxygen concentration at the impeller outlet. The maximal increments of absorbed oxygen in the suction chamber, impeller, and volute were 98%, 447%, and 694%, respectively, and the volume fractions were attenuated by 18.3%, 12.5%, and 5.0%, respectively. Notably, an increase in the gas volume fraction was the dominant reason for exacerbating the instability of the impeller forces, and the range of the radial force tended to be narrow and concentrated as the concentration increased.